The invention relates to a method and apparatus for plastifying and tearing up damaged road-surfaces and covers, distributing and profiling the broken-up material, combining and laying of the broken-up material with fresh bituminous mixture, and the final profiling and condensing of the two layers.
Such equipment, which has become known under the name of "REPAVER", was for the first time put into service in Germany in the district of the Autobohnamt Darmstadt and made known to the public by the Hessian Television in its evening show called "HESSENSCHAU" early in November 1975.
This repaver-equipment combines, in one mobile unit, a vertically adjustable breaker. Mounted in front and behind the breaker are heaters to plastify the road-top coat and to further temper the breaking-up or broken-up material. The unit also has a single-distribution worm and, mounted thereafter, a vertical dressing beam. A unit comprising a distribution worm and a vibration beam is mounted on the end of the bearing frame.
This unit picks up the mixture at its front in the direction of motion, carries it over its entire length, and directly feeds it into the paving unit, i.e., between the distribution worm and the vibration beam.
This procedure and the equipment necessary for performing this procedure have the following disadvantages: (a) The combination of the mentioned units, i.e., a breaker, 2 heating units, a coarse distribution, including a worm and a dresser beam for the loosened material and a paving unit, not only have a high structural weight -- and resulting therefrom, the necessity of power sources with high output -- but they define and finally limit the utility of the machine, which is dependent on the ground and underground conditions, or its working depth, since the power requirements for the actual breaking-up work in relation to the entire power requirements is significant.
The limitation of the surface removed to about 1.5cm at the most, as observed when working on federal high-ways, is in many cases not sufficient, to fully remedy dents, truck grooves, or other damages, so that only a removal of the ridges takes place. For the road builder this means that the new road cover is badly anchored to the incompletely roughened or broken-up under layers.
Due to the combination of the individual groupings into one mobile unit, this unit is very long so that it is impossible to work in small curve radii. Thus, the employment of the procedure is essentially limited to the repair or renewal of federal highways or similar major roads. (b) The limitation of the breaking-up depth to about 1.5cm, i.e., to the removal of the ridges only, does not provide a sufficient quantity of torn-up surface material for subsequent repaving (80 - 120 kg/m.sup.2). It has been observed that the total fresh-mixture output of the units is limited to about 50 kg/m.sup.2 due to the given total power of the apparatus. Hence, the repaving takes place only to an insufficient thickness, and an insufficient inner binding results as well as a low quality bonding to the underground. (c) The placing of a second heating unit immediately behind the breaking-up tool leads often to inflaming of the broken-up surface, or to their permanent burning - since heat is generated by the breaking-up procedure due to the burning out of the low boiling hydrocarbon components of the binder material, whereby the latter loses its gluing capacity for further bonding with the same material or with fresh mixtures or the readiness to bond is at least considerably reduced. (d) The machine is not suited to repave roads in developed housing areas, since the large number of road caps, for example, for water, gas, and telephone services, etc., requires the raising of the entire machine, since the individual elevations cannot be detoured nor can they be removed manually under the long mobile unit. (e) The pre-distribution of the broken-up mixture over the width and the laying of the broken-up material by the mentioned auxiliary means - worm and rake - is not sufficient for a compensation between the areas of an increased and those of a decreased removal, so that the material fed into the paving unit is unequal in its thickness as well as in its consistency, whereby the long way over the entire machine and the cooling off of the mixture connected therewith has to be regarded as a further disadvantage for a satisfactory repaving.
(f) The tires of the heavy unit run on the broken-up and heated asphalt thereby producing in their track a considerable pre-compaction of the loosened material as well as a different structure of the surface, which should actually be uniform in every respect for the fresh bituminous material.
The above method is known as the "repave"-procedure.
Procedures of similar type, i.e., the "peeling-off" and "milling-off" procedures are also known.
The old surface material is removed by milling or peeling off procedures for secondary purposes. The peeled or milled-off material has to be heated up after it has been crushed first according to the requirements and normally a softener and/or a small quantity of binding material of high penetration is added.
The disadvantages and deficiencies of the procedures described are so aggravating that one can regard these procedures only as interesting research-tests and not, however, as real instructions for the regeneration of bituminous road surfaces.